Since it was first discovered with the telescope of the Mount Wilson and Palomar Observatories then mentioned in [1]}, IC63 (see Fig. REF , top panel) has been the subject of various studies [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}. At the very beginning, [9]} found evidence of Extended Red Emission (ERE) in IC63, based on low-resolution UV (115-195 nm) spectra obtained with the International Ultraviolet Explorer (IUE) together with spectra obtained at the McGraw-Hill Observatory, which covers a spectral range from 500 to 900 nm. They estimated that the UV field hitting the surface of IC63 is about \(\sim 2.3 \times 10^{5}\)  photons cm s Hz\(^{-1}\)  at 100 nm, henceThe incident UV radiation field is there expressed in units \(\chi \)  of the [10]} average interstellar radiation field. \(\chi \sim 680\)  (i.e. \(G_{0}\)  \(\sim \)  1160). Using this \(\chi \)  value together with the IUE observations, [11]} found an average density of \(n\sim 4\times 10^{4}\)  H cm\(^{-3}\)  in this nebula. Based on millimeter and submillimeter observationsUsing the CSO (Caltech Submillimeter Observatory) telescope at Mauna Kea, the NRAO (National Radio Astronomical Observatory) 12 meter telescope at Kitt Peak, the IRAM (Institut de Radio Astronomie Millimétrique) 30 meter telescope at Pico Valeta and the JCMT (James Clerk Maxwell Telescope) 15 meter telescope at Mauna Kea., [12]} constrained the UV field as well as the average density in IC63 using HCO\(^+\) , CS, HCN, and H\(_2\) CO lines. They found that \(\chi \)  is about 650 (i.e. \(G_{0}\)  \(\sim \)  1110) and \(n(\mathrm {H_{2}})\sim (5\pm 2) \, \times 10^{4}\)  cm\(^{-3}\)  (\(n_{\mathrm {H}}\sim 2\,n(\mathrm {H_2})\sim 1\pm 0.4 \, \times 10^{5}\)  H cm\(^{-3}\) ). These results where later reinforced on the basis of chemical calculations for various physical conditions with \(n_{\mathrm {H}}\)  varying from \(6\times 10^{4}\)  and \(14\times 10^{4}\)  H cm\(^{-3}\) , [13]} found a best fit corresponding to \(n_{\mathrm {H}}\)  = \(1\times 10^{5}\)  H cm\(^{-3}\) . This value was confirmed in [14]} and they showed that the carbon abundance in gas-phase is \(X_{\mathrm {C}}=(13^{+6}_{-4})\)  % although it is about 30-60 % in diffuse clouds such as \(\zeta \)  Oph [15]}. Using H\(_2\)  pure-rotational lines with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) together with major fine-structure cooling lines of OI at 63 \(\mu \) m and 145 \(\mu \) m as well as CII at 157.7 \(\mu \) m, [16]} found that the incident radiation field has a \(G_{0}\)  of about \(10^{3}\) , which falls in the range of the \(G_{0}\)  values found in previous studies. Observations at IRAM 30-m of C\(_2\) H, c-C\(_3\) H\(_2\) , C\(_4\) H, l-C\(_3\) H, c-C\(_3\) H, and HN\(^{13}\) C with relatively high abundance might support an in situ formation of carbon chains and rings assisted by a release of acetylene from very small carbon particles [17]}, [18]} or the release of C\(_n\) H\(_m\)  species from the photo-processing of a-C(:H) nano-particles [19]}. Based on extinction mapping, evidence for dust evolution has been shown in IC63 [20]}.
As \(G_{0}\)  estimates vary between \(G_{0}\)  \(\sim 1000\)  [16]} and \(G_{0}\)  \(\sim 1200\)  [9]}, [12]}, we chose \(G_{0}\)  = 1100.
